Common Mistakes of English Grammar, Mechanics, and Punctuation

Dr. Jeffrey Kahn, Illinois State University

The following illustrate some common mistakes made in papers written by
college students. This is by no means an exhaustive list of all of the
mistakes that could be made with respect to grammar, mechanics, and punctuation.
Rather, this is a list of some of the more common mistakes that occur.

Avoid using sexist wording, such as "he" or "his" when you are trying
to refer to both boys and girls or to both women and men.

Wrong: When the subject reported being finished, the experimenter
asked
him to complete a second questionnaire.

Right: When the subject reported being finished, the experimenter
administered
a second questionnaire.

Do not combine singular and plural forms of words in the same sentence.

Wrong: Each subject rated their own mood on the questionnaire.

Right: Each subject rated his or her own mood on the questionnaire.

Right: All subjects rated their own moods on
the questionnaire.

Wrong: A variety of issues were presented at the meeting.

Right: A variety of issues was presented at the meeting.

Use commas when appropriate. Sometimes a comma should be omitted,
whereas other times including a comma may help to improve your writing.

Use a comma when separating main clauses:

Wrong: We are here on this planet once and we might as well
get a feel for the place.

Right: We are here on this planet once, and we might as well
get a feel for the place.

Set off parenthetical material within commas.

Wrong: Sometimes people gossip as Barbara Walters has observed
because they want to be interesting.

Right: Sometimes people gossip, as Barbara Walters has observed,
because they want to be interesting.

Right: The Air Force debunked UFO sightings, but millions
of Americans didn't listen.

Do not write fragmented sentences. Every sentence needs a subject
and a predicate.

Wrong: And for days tried to change my mind. (no subject)

Right: For days he/she/it tried to change my mind.

Do not confuse "its" and "it's." "Its" is the possessive form of
"it," whereas "it's" is a contraction for "it is."

Wrong: Its time for a change.

Right: It's time for a change.

Wrong: What is it's purpose?

Right: What is its purpose?

Do not confuse "effect" and "affect." "Effect" is typically a noun, meaning
some consequence or result. "Affect" is typically a verb, meaning to bring about
an effect. (But note that "affect" also can be a noun meaning emotional expression, and
"effect" can be used as a verb to mean to cause something to come into being.)

Wrong: The experimental manipulation caused an interesting affect.

Right: The experimental manipulation caused an interesting effect.

Wrong: The intervention did not effect the behavior of
the therapy group.

Right: The intervention did not affect the behavior of
the therapy group.

Use apostrophes in the appropriate place to indicate possession.
A word ending in "s" has an apostrophe at the end of the word; otherwise,
place an apostrophe followed by "s" to indicate possession.

Wrong: The student's faculty advisor was very committed to
their
learning.

Right: The students' faculty advisor was very committed to
their
learning. (if more than one student)

Right: The student's faculty advisor was very committed to
her
learning. (if only one female student)

Do not use an apostrophe to indicate a plural form of a word. Only
use it to indicate possession.

Wrong: The student's all have busy schedules.

Right: The students all have busy schedules.

Use a hyphen when using two words to act as one adjective (unless
the first word ends in -ly).

Wrong: The college student sample was smarter than the high
school sample.

Right: The college-student sample was smarter than the high-school
sample.